In the medical and dental fields, walls, floors, examination chairs and tables, other equipment, and instruments used in examination and treatment are contaminated by various organic materials which contain or support the growth of various microorganisms. Cleaning alone is not sufficient to kill or inhibit the growth of these organisms and use of disinfectants is necessary.
A disinfectant is a substance which destroys or irreversibly inactivates infectious or other undesirable bacteria, pathogenic fungi, and viruses or surfaces or inanimate objects. Disinfectants kill the growing forms but not necessarily the resistant spore forms of microorganisms. Sterilizers, on the other hand, destroy the growing and spore forms of viruses, bacteria, and fungi on inanimate surfaces. Sanitizers are used to reduce the number of living bacteria or viable virus particles or inanimate surfaces, in water, or in air, and fungicides and fungistats are used to inhibit the growth of or destroy fungi on inanimate surfaces.
It has become common practice to use glutaraldehyde solutions as surface disinfectants or sterilants in dental and medical facilities. However, while glutaraldehyde solutions are an effective disinfectant, there are many drawbacks to the use of glutaraldehyde, including safety concerns, problems with storing the large volumes of solutions required, and the limited shelf stability of solutions. In addition, if the glutaraldehyde solution is prepared by dilution of a concentrated solution there is the inconvenience of measuring and pouring the liquid concentrate.
The use of disinfectant or sterilant concentrates in a powdered form has been taught in the prior art; for example, in U.S. Pat. No. 5,350,563 to Kralovic et al. The problem with the use of powders as disinfectant concentrates is that they also must be measured in order to prepare the diluted solution and must be poured from one container to another. In addition, there are sometimes problems with forcing the powder into solution.
Another problem faced when using liquid or powdered concentrates is that many of the ingredients used for disinfectants can be harmful to humans and the handling of concentrated amounts of these ingredients can be even more harmful. Care must be taken not to spill or come into contact with any concentrate and not to inhale any dust from powdered concentrates.
Other patents, for example, those of Hunt et al., U.S. Pat. No. 4,265,847, and White et al., U.S. Pat. No. 4,536,389, teach effervescent tablets useful for preparing solutions for sterilizing or disinfecting. Such compositions are rapid water soluble tablets typically comprising an active chemical compound, an alkali metal bicarbonate, e.g. sodium or potassium bicarbonate, and a solid alipHatic carboxylic acid such as citric acid, tartaric acid, adipic acid, or an acid salt thereof. In use, such tablets are dissolved in water whereupon the interaction of the bicarbonate and acid components results in the release of carbon dioxide, thus increasing the rate of solution of the other components and producing a solution in which the active (disinfecting) ingredient is homogenously dissolved. Methods for forming effervescent tablets are well known in the art. For example, see U.S. Pat. No. 4,265,847 to Hunt et al. and U.S. Pat. No. 5,114,647 to Levesque et al., which disclosures are incorporated herein in their entireties, by reference.
Halogen compounds are effective as disinfecting agents but their use as such agents is limited due to difficulties in storage, mixing, and handling of concentrated halogens and instability of dilute forms. The use of sodium dichloroisocyanurate as a disinfecting agent is known in the prior art. For example, see U.S. Pat. No. 4,536,389, to White et al., and U.S. Pat. No. 5,114,642, to Levesque et al. Sodium dichloroisocyanurate hydrolyses in water to produce hypochlorous acid (HOCI) and hypochlorite (OCl.sup.-), which exist in solution at an equilibrium that is dependent upon the pH of the solution. For example, as shown in FIG. 1, at neutral pH a solution consists of about 75% hypochlorous acid and 25% hypochlorite. The prior art teaches the use of bromide as a disinfectant, the hypobromous acid and hypobromite species are produced in solution typically by the use of bromo, chloro-5,5-dimethylhydantoin. The hypohalous acid specie is the antimicrobial form of the above compounds, with the hypohalite having some antimicrobial effect. However, the negative charge of the hypohalite inhibits its diffusion through the cell wall for microorganisms and thus lowers its antimicrobal effect.
Chloride and bromide have difference equilibriums in solution, as shown by the chart of FIG. 1. The dissociation characteristics of hypobromous acid are such that the hypobromous acid is the predominant species over hypobromite up to a pH of about 8.3, which is the point when the concentrations of hypobromous acid and hypobromite are about equivalent. However, hypochlorous acid is a predominant species over hypochlorite only up until a pH of about 7.4. At a pH above about 6.0, as shown by FIG. 1, a solution of hypobromous acid is a much more effective disinfectant because more of the hypohalite species is present. Furthermore, in addition to the greater percentage of hypobromous acid compared to hypobromite, hypobromous acid is a stronger antimicrobial agent than hypochlorite acid, as shown by FIG. 2.
Accordingly, there is a need for an effective disinfecting or sterilant agent packaged and supplied in a convenient effervescent form. The effervescent tablet must fully dissolve in a rapid fashion to form a homogeneous disinfecting solution which is highly active and stable for a useful length of time.